Vegetation productivity soil reclamation equations for the North Dakota coal fields.

Abstract

The dissertation addresses the development of an agricultural productivity equation within a landscape planning and modeling context for the North Dakota coal fields in Oliver, Mercer, and Dunn counties. The procedure employed principal component analysis to develop a combined vegetation yield variable from spring wheat, barley, oat, grass/legume, Eastern red cedar, ponderosa pine, green ash, Siberian peashrub, American plum, and common chokecherry. Soil variables were weighted according to a depth weighting formula and then examined in regression analysis to predict vegetation yield. Eleven equations were developed in the study. The coal zone equation was selected as the best equation to predict plant growth in the surface mining portion of the study area (R$\sp2$ = 66.06 and an overall p-value of 0.0001). The regressors included in the coal zone equation were available water holding capacity, percent slope, percent rock fragments, topographic position squared, hydraulic conductivity squared, percent organic matter squared, percent clay times topographic position, available water holding capacity times percent rock fragments, hydraulic conductivity times percent slope, soil reaction times topographic position, electrical conductivity times topographic position, percent organic matter times topographic position, percent organic matter times electrical conductivity, and a Y intercept coefficient. The regression coefficients were stable under bootstrap and jackknife evaluation procedures and worked relatively well with a subsampling procedure. The equation correlated moderately with reclaimed soil field trials. In addition the study identified a set of sandy loam soils conducive for vegetation growth as well as for supporting buildings. As a set of general guidelines, the coal zone equation indicated the most productive soil configurations include a middle topographic position, gentle nearly level slopes, no rock fragments, a soil reaction near 7.5, soil organic matter near 0.75%, 25% clay content, moderate hydraulic conductivity rates, and maximized available water holding capacity. The guidelines and coal zone equation may be employed to assist landscape reclamation planning efforts and can be adopted in regulatory standards to evaluate soil reconstruction profiles.